Armor systems

ABSTRACT

An armor system useful, for example, as a shroud, comprising a first pliable, cut resistant fibrous layer and a second pliable fibrous layer is disclosed. The first layer is arranged to receive an impact from a large projectile prior to the second layer and engages the projectile to slow its velocity. The second layer is substantially coextensive with the first and dissipates the incoming energy of the impact to resist complete penetration of the second layer by the projectile, preferably by deforming in response to the impact. Both layers comprise fibers having a tensile modulus of at least about 200 g/d, and an energy-to-break of at least about 8 J/g and a tenacity equal to or greater than about 10 g/d. In another embodiment, the layers are reversed relative to the impact face of the system so that the second layer becomes the first layer and is resistant to projectiles impacting the system, while the first layer becomes the second layer and resists deformation of the system by projectile impacts. Any projectile which completely penetrates the first layer is engaged by the second layer to slow its velocity and prevent complete penetration of the second layer. This armor system provides excellent ballistic resistance with enhanced deformation control.

This application is a continuation of application Ser. No. 490,179 filedMar. 8, 1990 now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to armor systems. More particularly, thepresent invention relates to a first multi-layer armor system which canbe a shroud for the containment of large, high velocity cuttingprojectiles, and to a second multi-layer armor system which is highvelocity impact/ballistic resistant and minimizes deformation andpenetrations from such an impact.

2. Prior Art

In the summer of 1989, a blade/blade fragment broke away from theturbine engine of an airborne aircraft and severed the aircraft'shydraulic system. The aircraft crash-landed soon after. Shrouds tocontain flying blade fragments (projectiles) from a failed turbineengine to protect vital equipment in close proximity are known--theseshrouds are formed from multiple layers of loosely woven aramid, such asKevlar®, fabric. Similarly, shields to protect aircraft engines fromdamage by flying fragments from a source external to the engine areknown; these can be soft armor shields formed from layers of wovenaramid fabric, metal shields, or a combination of the two (see U.S. Pat.No. 4,057,359, hereby incorporated by reference).

In either event, with the number of woven fabric layers heretoforeutilized, these prior art shrouds/shields are not as effective withrespect to high velocity cutting impacts of a rapidly rotating engineblade which fractures and is hurled away from the higher power, largerengines of today. An obvious solution would be to increase the number offabric layers. However, this solution suffers the same disadvantage ofsome of the metallic shields available, excessive weight and expense.Therefore, a lightweight armor system which could function as aprojectile containing shroud is desirable. Such an armor system wouldhave utility in many areas, i.e., wherever there is a potential forfailure of equipment with high speed moving parts that could break intolarge fragments and become high velocity projectiles that cut and teartheir way through adjacent parts/machinery.

Applicants have discovered such an armor system, and in the course ofsuch discovery have also discovered a ballistic resistant armor systemwhich minimizes armor deformation after a high velocity impact orballistic impact. An armor system can stop an impacting object fromcompletely penetrating the system and yet deform (or bulge) so badly onits non-impact side that damage occurs to the equipment or person beingprotected by the armor system.

Ballistic resistant articles such as vests, helmets, hard and softarmor, structural members of helicopters and other military equipment,vehicle panels, briefcases, raincoats and umbrellas containing highstrength fibers are known. Fibers conventionally used in these articlesinclude aramid fibers such as poly(p-phenylene terephthalamide),graphite fibers, nylon fibers, ceramic fibers, high strengthpolyethylene fibers, e.g., SPECTRA®, glass fibers and the like For manyapplications, such as vests or parts of vests, the fibers are used in awoven or knitted fabric.

U.S. Pat. No. 4,623,574 discloses the formation of prepreg sheetscomprised of elastomer coated high strength fibers which aresubstantially parallel and aligned along a common fiber direction. Thepatent teaches that the prepreg sheets can be plied together, withsuccessive sheets being rotated relative to the first sheet, to formsimple composite materials.

U.S. Pat. No. 4,181,768 teaches lightweight, rigid armor formed by presslaminating alternating layers of 6,6 nylon film and aramid fabric. Thefabric can be a nonwoven such as a needle punched felt.

U.S. Pat. No. 4,574,105 teaches a flexible, penetration resistant panelcomprised of face plies of woven poly(p-phenylene terephthalamide) andbacking plies of nonwoven polyamide, preferably needled polyamide felt.This patent teaches that the reverse configuration (face plies ofpolyamide felt backed with woven Kevlar fiber plies) decreases theballistic limit velocity by 200 ft/sec. U.S. Pat. No. 4,608,717 teachesa flexible, protective armor comprising layers of aramid fiber fabricwhich sandwich a trauma attenuation layer of feathers, foam or felt. Thelayers are drawn together, preferably by stitching. There is no teachingof a felt comprising fiber with high tensile properties.

U.S. Pat. No. 4,623,574, commonly assigned, teaches a ballisticresistant composite comprising a network of high strength fibers whichare substantially coated with an elastomeric matrix material. U.S. Pat.No. 4,737,401, also commonly assigned, teaches a ballistic resistantarticle which comprises at least one network of high strength extendedchain polyethylene, polypropylene, polyvinyl alcohol orpolyacrylonitrile fiber having a denier of not more than 500 and atensile modulus of at least about 200 g/denier. In both of thesepatents, the network can be a felt.

U.S. Pat. No. 4,660,223 teaches body armor comprising an assemblage ofpanels, each panel consisting of an inner face ply of titanium metalbonded to a strike face ply of aramid fiber woven cloth. The assemblageof panels is held in a predetermined relationship by first and secondlayers of felt material, preferably of aramid fibers, which are bondedwith adhesive plies to the inner and strike faces of the panels. Thefelt plies permit the panels to move relative to one another and thusavoid inhibiting body movement of the wearer.

U.S. Pat. No. 4,681,792, commonly assigned, teaches a flexible ballisticresistant article having first and second portions each comprising aplurality of fibrous layers where the resistance to displacement offibers in each layer of the second portion is greater than that of eachlayer in the first portion. The layers of the first portion consistessentially of uncoated fibers comprising fiber selected from the groupof polyolefin fibers, polyvinyl alcohol fibers and polyacrylonitrilefibers having a tensile modulus of at least 300 g/d and a tenacity of atleast about 15 g/d, and the layers of the second portion consistessentially of uncoated fibers. According to the patent, woven fibrouslayers exhibit a higher resistance to fiber displacement than nonwovenlayers.

The present invention, was developed in an attempt to overcome thedeficiencies of the prior art.

BRIEF DESCRIPTION OF THE INVENTION

The present invention provides an armor system, preferably soft,comprising a first pliable, cut resistant fibrous layer and a secondpliable, impact/ballistic energy absorbing fibrous layer. The firstlayer is arranged to receive an impact from a large projectile prior tothe second layer and engages the projectile to slow its velocity. Thesecond layer is substantially coextensive with the first layer anddissipates the incoming energy of the impact to resist completepenetration of the second layer by the projectile, preferably bydeforming and acting in response to the impact. Both layers comprisefibers having a tensile modulus of at least about 200 g/d, and anenergy-to-break of at least about 8 J/g and a tenacity equal to orgreater than about 10 g/d.

This armor system is not only effective at containing large, highvelocity cutting projectiles but also regular ammunition. Otheradvantages of this invention are higher performance over the prior artas well as a weight reduction on the order of 30% (for same fibertypes).

The present invention also provides an improved jet engine system thatincludes a jet engine and a nacelle. The improvement is an armor systemcomprising a first pliable, cut resistant fibrous layer and a secondpliable fibrous layer substantially coextensive with the first layer.The second layer is located closer to the nacelle than the first layer,and the first layer is located closer to the jet engine than the secondlayer. The first layer engages any projectile thrown by said engine toslow its velocity. The second layer dissipates the incoming energy tothe impact to resist complete penetration of the second layer by theprojectile. Both layers comprise fibers having a tensile modulus of atleast about 200 g/d, and an energy-to-break of at least about 8 J/g anda tenacity equal to or greater than about 10 g/d.

In an alternate jet engine system that includes a jet engine and anacelle, the improvement is also an armor system comprising a firstpliable, cut resistant fibrous layer and a second pliable fibrous layersubstantially coextensive with the first layer. The second layer islocated closer to the nacelle than the first layer, and the first layerbeing located closer to the jet engine than the second layer. The firstlayer comprises a plurality of networks selected from the groupconsisting of an uncoated nonwoven network of randomly oriented fibersand an uncoated knitted, preferrably tightly, network of fibers. Thesecond layer comprises a plurality of networks selected from the groupconsisting of a loosely woven network of fibers, an open knitted networkof fibers, a braided network of fibers, and a nonwoven network oforiented fibers. Both layers again comprise fibers having a tensilemodulus of at least about 200 g/d, and an energy-to-break of at leastabout 8 J/g and a tenacity equal to or greater than about 10 g/d.

In the course of developing this armor system, applicants furtherdiscovered that when the layers are arranged so that the second layerreceives an impact from a projectile first, followed by the first layer,then the system has excellent high velocity impact or ballisticresistance with even less deformation of the non-impact layer. In thissystem, the first layer (the second layer of the embodiment previouslydescribed) is arranged to receive an impact from a projectile prior tothe second layer (the first layer of the embodiment previouslydescribed). The first layer is resistant to the impact, and the secondlayer minimizes deformation of the system by the projectile impact tothe first layer. Furthermore, any projectile which completely penetratesthe first layer is engaged by the second layer to slow its velocity andprevent complete penetration of the second layer. Both layers comprisefibers having a tensile modulus of at least about 200 g/d, an energy tobreak of at least 8 J/g and a tenacity equal to or greater than about 10g/d.

This second armor system is advantageously used against smallerprojectiles/fragments, but is ineffective alone against the large, highvelocity cutting projectiles which can be contained by the systempreviously described. These smaller projectiles/fragments may even befrom explosions and have velocities similar to or lower than the largeprojectiles. For vests, blunt trauma can be reduced by this system.

The two described systems can be used in conjunction with one another,as long as weight constraints permit, to provide a system capable ofstopping a large, high velocity cutting projectile regardless of impactface and also of resisting a ballistic threat with minimum deformation.Such a system would minimally comprise three layers, the first and thirdof which are like those of the first layer of the first armor systemdescribed above, and the second of which is like the second layer of thefirst armor system described above. The second layer is sandwichedbetween the first and third layers for this third embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings,

FIGS. 1 and 1A are perspective views of a corner of an armor system ofthe first embodiment;

FIGS. 2 and 2A are perspective views of a corner, one layer of which ispartially cut away, of an armor system of either the first or secondembodiment depending upon the orientation of the layers with respect tothe impacting object;

FIG. 3 is a perspective view of a corner of an armor system of the thirdembodiment of this invention; and

FIG. 4 is a partially cut away perspective view of a high bypass jetengine with the shroud of the present invention in place.

DETAILED DESCRIPTION OF THE INVENTION

By fiber is meant an elongate body, the length dimension of which ismuch greater than the transverse dimensions of width and thickness.Accordingly, the term fiber includes monofilament, multifilament,ribbon, strip, staple and other forms of chopped, cut or discontinuousfiber and the like having regular or irregular cross-sections. Fiber andfilament are used interchangeably hereafter.

By network is meant tapes or fibers arranged in configurations ofvarious types. For example, the plurality of fibers can be groupedtogether to form a twisted or untwisted yarn. The fibers of yarn may beformed as a felt, knitted or woven (plain, basket, satin and crow feetweaves, etc.) into a network, fabricated into a non-woven fabric (randomor ordered orientation), arranged in a parallel array, layered, orformed into a fabric by any of a variety of conventional techniques.

The cross-sections of fibers for use in this invention may vary widely.They may be of circular or of flat or of oblong or of irregular orregular multi-lobal cross-section having one or more regular orirregular lobes projecting from the linear or longitudinal axis of thefilament. It is particularly preferred that the fibers be ofsubstantially circular, flat or oblong cross-section, most preferablythe former.

The diameter of the fibers and the thickness of the network may varywidely. In general, the smaller the diameter and the thinner thenetwork, the greater the ballistic protection provided; and conversely,the greater the diameter of the fiber and the greater the thickness ofthe networks, the lower the ballistic protection provided.

The type of fibers used may vary widely and can be metallic,semi-metallic, inorganic and/or organic fibers. It is crucial, however,that a sufficient weight percent of cut resistant fibers or combinationof fibers with high tensile properties be used to achieve the indicatedproperties of the layers of the armor systems. Other fibers, however,may be included by blending for a variety of reasons. Fibers having thehigh tensile properties desired are those having a tenacity equal to orgreater than about 10 g/d, a tensile modulus equal to or greater thanabout 200 g/d and an energy-to-break equal to or greater than about 8Joules/gram (J/g). Preferred fibers are those having a tenacity equal toor greater than about 15 g/d, a tensile modulus equal to or greater thanabout 300 g/d and an energy-to-break equal to or greater than about 20J/g. Particularly preferred fibers are those having a tenacity equal toor greater than about 16 g/d, a tensile modulus equal to or greater thanabout 400 g/d, and an energy-to-break equal to or greater than about 27J/g. Amongst these particularly preferred embodiments, most preferredare those embodiments in which the tenacity of the fibers is equal to orgreater than about 22 g/d, the tensile modulus is equal to or greaterthan about 900 g/d, and the energy-to-break is equal to or greater thanabout 27 J/g. In the practice of this invention, fibers of choice have atenacity equal to or greater than about 35 g/d, the tensile modulus isequal to or greater than about 1500 g/d and the energy-to-break is equalto or greater than about 50 J/g.

Illustrative of useful organic filaments are those composed ofpolyesters, polyolefins, polyetheramides, fluoropolymers, polyethers,celluloses, phenolics, polyesteramides, polyurethanes, epoxies,aminoplastics, silicones, polysulfones, polyetherketones,polyetheretherketones, polyesterimides, polyphenylene sulfides,polyether acryl ketones, poly(amideimides), and polyimides. Illustrativeof other useful organic filaments are those composed of aramids(aromatic polyamides), such as poly(m-xylylene adipamide),poly(p-xylylene sebacamide), poly(2,2,2-trimethyl-hexamethyleneterephthalamide), poly(piperazine sebacamide), poly(metaphenyleneisophthalamide) (Nomex) and poly(p-phenylene terephthalamide) (Kevlar);aliphatic and cycloaliphatic polyamides, such as the copolyamide of 30%hexamethylene diammonium isophthalate and 70% hexamethylene diammoniumadipate, the copolyamide of up to 30% bis(-amidocyclohexyl)methylene,terephthalic acid and caprolactam, polyhexamethylene adipamide (nylon66), poly(butyrolactam) (nylon 4), poly(9-aminonoanoic acid) (nylon 9),poly(enantholactam) (nylon 7), poly(capryllactam) (nylon 8),polycaprolactam (nylon 6), poly(p-phenylene terephthalamide),polyhexamethylene sebacamide (nylon 6,10), polyaminoundecanamide (nylon11), polydodecanolactam (nylon 12), polyhexamethylene isophthalamide,polyhexamethylene terephthalamide, polycaproamide, poly(nonamethyleneazelamide (nylon 9,9), poly(decamethylene azelamide) (nylon 10,9),poly(decamethylene sebacamide) (nylon 10,10),poly[bis-(4-aminocyclohexyl)methane 1,10-decanedicarboxamide]cycloaliphatic and aromatic polyesters such as poly(1,4-cyclohexylidenedimethyl eneterephthalate) cis and trans,poly(ethylene-1,5-naphthalate), poly(ethylene-2,6-naphthalate),poly(1,4-cyclohexane dimethylene terephthalate) (trans),poly(decamethylene terephthalate), poly(ethylene terephthalate),poly(ethylene isophthalate), poly(ethylene oxybenzoate),poly(para-hydroxy benzoate), poly(dimethylpropiolactone),poly(decamethylene adipate), poly(ethylene succinate), poly(ethyleneazelate), poly(decamethylene sabacate), poly(α,α-dimethylpropiolactone),and the like.

Also illustrative of useful organic filaments are those of liquidcrystalline polymers such as lyotropic liquid crystalline polymers whichinclude polypeptides such as poly -benzyl L-glutamate and the like;aromatic polyamides such as poly(1,4-benzamide),poly(chloro-1-4-phenylene terephthalamide), poly(1,4-phenylenefumaramide), poly(chloro-1,4-phenylene fumaramide),poly(4,4'-benzanilide trans, trans-muconamide), poly(1,4-phenylenemesaconamide), poly(1,4-phenylene) (trans-1,4-cyclohexylene amide),poly(chloro-1,4-phenylene) (trans-1,4-cyclohexylene amide),poly(1,4-phenylene 1,4-dimethyl-trans-1,4-cyclohexylene amide),poly(1,4-phenylene 2.5-pyridine amide), poly(chloro-1,4-phenylene2.5-pyridine amide), poly(3,3'-dimethyl-4,4'-biphenylene 2.5 pyridineamide), poly(1,4-phenylene 4,4'-stilbene amide),poly(chloro-1,4-phenylene 4,4'-stilbene amide), poly(1,4-phenylene4,4'-azobenzene amide), poly(4,4'-azobenzene 4,4'-azobenzene amide),poly (1,4-phenylene 4,4'-azoxybenzene amide), poly(4,4'-azobenzene4,4'-azoxybenzene amide), poly (1,4-cyclohexylene 4,4'-azobenzeneamide), poly(4,4'-azobenzene terephthal amide), poly(3,8-phenanthridinone terephthal amide), poly(4,4'-biphenyleneterephthal amide), poly(4,4'-biphenylene 4,4'-bibenzo amide),poly(1,4-phenylene 4,4'-bibenzo amide), poly(1,4-phenylene4,4'-terephenylene amide, poly(1,4-phenylene 2,6-naphthal amide),poly(1,5-amide), poly(1,4-phenylene 2,6-naphthal amide) ,poly(1,5-naphthalene terephthal amide), poly(3,3'-dimethyl-4,4-biphenylene terephthal amide), poly(3,3'-dimethoxy-4,4'-biphenyleneterephthal amide), poly(3,3'-dimethoxy-4,4-biphenylene 4,4'-bibenzoamide) and the like; polyoxamides such as those derived from2,2'-dimethyl-4,4'-diamino biphenyl and chloro-1,4-phenylene diamine;polyhydrazides such as poly chloroterephthalic hydrazide, 2,5-pyridinedicarboxylic acid hydrazide) poly(terephthalic hydrazide),poly(terephthalicchloroterephthalic hydrazide) and the like;poly(amidehydrazides) such as poly(terephthaloyl 1,4 aminobenzhydrazide)and those prepared from 4-aminobenzhydrazide, oxalic dihydrazide,terephthalic dihydrazide and para-aromatic diacid chlorides; polyesterssuch as those of the compositions includepoly(oxy-trans-1,4-cyclohexyleneoxycarbonyl-trans-1,4-cyclohexylenecarbonyl-b-oxy-1,4-phenyleneoxyteraphthaloyl)and polypoly(oxy-cis-1,4-cyclohexyleneoxycarbonyl-trans-1,4-cyclohexylenecarbonyl-b-oxy-1,4-phenyleneoxyterephthaloyl)in methylene chloride-o-cresol poly(oxy-trans-1,4-cyclohexyleneoxycarbonyl-trans-1,4-cyclohexylenecarbonyl-b-oxy-(2-methyl-1,4-phenylene)oxy-terephthaloyl)in 1,1,2,2-tetrachloroethane-o-chlorophenol-phenol (60:25:15vol/vol/vol),poly[oxy-trans-1,4-cyclohexyleneoxycarbonyl-trans-1,4-cyclohexylenecarbonyl-b-oxy(2-methyl-1,3-phenylene)oxy-terephthaloyl]in o-chlorophenol and the like; polyazomethines such as those preparedfrom 4,4'-diaminobenzanilide and terephthalaldephide,methyl-1,4-phenylenediamine and terephthalaldehyde and the like;polyisocyanides such as poly(α-phenyl ethyl isocyanide), poly(n-octylisocyanide) and the like; polyisocyanates such as poly(n-alkylisocyanates) as for example poly(n-butyl isocyanate), poly(n-hexylisocyanate) and the like; lyotropic crystalline polymers withheterocyclic units such as poly(1,4-phenylene-2,6-benzobisthiazole)(PBT), poly(1,4-phenylene-2,6-benzobisoxazole) (PBO),poly(1,4-phenylene-1,3,4-oxadiazole),poly(1,4-phenylene-2,6-benzobisimidazole), poly[2,5(6) -benzimidazole](AB-PBI) , poly[2,6-(1,4-phenylene-4-phenylquinoline]poly[1,1'-(4,4'-biphenylene)-6,6'-bis(4-phenylquinoline) ] and the like;polyorganophosphazines such as polyphosphazine,polybisphenoxyphosphazine, poly[bis(2,2,2' trifluoroethylene)phosphazine] and the like; metal polymers such as those derived bycondensation of trans-bis (tri-n-butylphosphine)platinum dichloride witha bisacetylene ortrans-bis(tri-n-butylphosphine)bis(1,4-butadinynyl)platinum and similarcombinations in the presence of cuprous iodine and an amide; celluloseand cellulose derivatives such as esters of cellulose as for exampletriacetate cellulose, acetate cellulose, acetate butyrate cellulose,nitrate cellulose, and sulfate cellulose, ethers of cellulose as forexample, ethyl ether cellulose, hydroxymethyl ether cellulose,hydroxypropyl ether cellulose, carboxymethyl ether cellulose, ethylhydroxyethyl ether cellulose, cyanoethylethyl ether cellulose,ether-esters of cellulose as for example acetoxyethyl ether celluloseand benzoyloxypropyl ether cellulose, and urethane cellulose as forexample phenyl urethane cellulose; thermotropic liquid crystallinepolymers such as celluloses and their derivatives as for examplehydroxypropyl cellulose, ethyl cellulose propionoxypropyl cellulose;thermotropic copolyesters as for example copolymers of6-hydroxy-2-naphthoic acid and p-hydroxy benzoic acid, copolymers of6-hydroxy-2-naphthoic acid, terephthalic acid and p-amino phenol,copolymers of 6-hydroxy-2-naphthoic acid, terephthalic acid andhydroquinone, copolymers of 6-hydroxy-2-naphthoic acid, p-hydroxybenzoic acid, hydroquinone and terephthalic acid, copolymers of2,6-naphthalene dicarboxylic acid, terephthalic acid, isophthalic acidand hydroquinone, copolymers of 2,6-napthalene dicarboxylic acid andterephthalic acid, copolymers of p-hydroxybenzoic acid, terephthalicacid and 4,4'-dihydroxydiphenyl, copolymers of p-hydroxybenzoic acid,terephthalic acid, isophthalic acid and 4,4'-dihydroxydiphenyl,p-hydroxybenzoic acid, isophthalic acid, hydroquinone and4,4'-dihydroxybenzophenone, copolymers of phenylterephthalic acid andhydroquinone, copolymers of chlorohydroquinone, terephthalic acid andp-acetoxy cinnamic acid, copolymers of chlorohydroquinone, terephthalicacid and ethylene dioxy-4,4'-dibenzoic acid, copolymers of hydroquinone,methylhydroquinone, p-hydroxybenzoic acid and isophthalic acid,copolymers of (1-phenylethyl)hydroquinone, terephthalic acid andhydroquinone, and copolymers of poly(ethylene terephthalate) andp-hydroxybenzoic acid; and thermotropic polyamides and thermotropiccopoly(amide-esters).

Also illustrative of useful organic filaments are those composed ofextended chain polymers formed by polymerization of α,β-unsaturatedmonomers of the formula:

    R.sub.1 R.sub.2 --C═CH.sub.2

wherein:

R₁ and R₂ are the same or different and are hydrogen, hydroxy, halogen,alkylcarbonyl, carboxy, alkoxycarbonyl, heterocycle or alkyl or aryleither unsubstituted or substituted with one or more substituentsselected from the group consisting of alkoxy, cyano, hydroxy, alkyl andaryl. Illustrative of such polymers of α,β-unsaturated monomers arepolymers including polystyrene, polyethylene, polypropylene,poly(1-octadecene), polyisobutylene, poly(1-pentene),poly(2-methylstyrene), poly(4-methylstyrene), poly(1-hexene),poly(4-methoxystyrene), poly(5-methyl-1-hexene), poly(4-methylpentene),poly(1-butene), polyvinyl chloride, polybutylene, polyacrylonitrile,poly(methyl pentene-1), poly(vinyl alcohol), poly(vinylacetate),poly(vinyl butyral), poly(vinyl chloride), poly(vinylidene chloride),vinyl choloride-vinyl acetate chloride copolymer, poly(vinylidenefluoride), poly(methyl acrylate), poly(methyl methacrylate),poly(methacrylonitrile), poly(acrylamide), poly(vinyl fluoride),poly(vinyl formal), poly(3-methyl-1-butene) , poly(4-methyl-1-butene),poly(4-methyl-1-pentene), poly(1-hexane), poly(5-methyl-1-hexene),poly(1-octadecene), poly(vinyl cyclopentane), poly(vinylcyclohexane),poly(a-vinylnaphthalene), poly(vinyl methyl ether),poly(vinylethylether), poly(vinyl propylether), poly(vinyl carbazole),poly(vinyl pyrrolidone), poly(2-chlorostyrene), poly(4-chlorostyrene),poly(vinyl formate), poly(vinyl butyl ether), poly(vinyl octyl ether),poly(vinyl methyl ketone), poly (methylisopropenyl ketone), poly(4-phenylstyrene) and the like.

Illustrative of useful inorganic filaments for use in the presentinvention are glass fibers such as fibers formed from quartz, magnesiaalumuninosilicate, non-alkaline aluminoborosilicate, soda borosilicate,soda silicate, soda lime-aluminosilicate, lead silicate, non-alkalinelead boroalumina, non-alkaline barium boroalumina, non-alkaline zincboroalumina, non-alkaline iron aluminosilicate, cadmium borate, aluminafibers which include "saffil" fiber in eta, delta, and theta phase form,asbestos, boron, silicone carbide, graphite and carbon such as thosederived from the carbonization of polyethylene, polyvinylalcohol, saran,aramid, polyamide, polybenzimidazole, polyoxadiazole, polyphenylene,PPR, petroleum and coal pitches (isotropic), mesophase pitch, celluloseand polyacrylonitrile, ceramic fibers, metal fibers as for examplesteel, aluminum metal alloys, and the like.

In the preferred embodiments of the invention, the networks arefabricated from high molecular weight polyethylene filament, highmolecular weight polypropylene filament, aramid filament, high molecularweight polyvinyl alcohol filament, high molecular weightpolyacrylonitrile filament, liquid crystalline polymer filament ormixtures thereof.

U.S. Pat. No. 4,457,985, hereby incorporated by reference, generallydiscusses such high molecular weight polyethylene and polypropylenefilaments. In the case of polyethylene, suitable filaments are those ofmolecular weight of at least 150,000, preferably at least 300,000, morepreferably at least one million and most preferably between two millionand five million. Such extended chain polyethylene (ECPE) filaments maybe grown in solution as described in U.S. Pat. No. 4,137,394 or U.S.Pat. No. 4,356,138, or may be a filament spun from a solution to form agel structure, as described in German Off. 3 004 699 and GB 20512667,and especially described in U.S. Pat. No. 4,551,296, also herebyincorporated by reference. As used herein, the term polyethylene shallmean a predominantly linear polyethylene material that may contain minoramounts of chain branching or comonomers not exceeding 5 modifying unitsper 100 main chain carbon atoms, and that may also contain admixedtherewith not more than about 50 weight percent of one or more polymericadditives such as alkene-1-polymers, in particular low densitypolyethylene, polypropylene or polybutylene, copolymers containingmono-olefins as primary monomers, oxidized polyolefins, graft polyolefincopolymers and polyoxymethylenes, or low molecular weight additives suchas antioxidants, lubricants, ultraviolet screening agents, colorants andthe like which are commonly incorporated by reference. Depending uponthe formation technique, the draw ratio and temperatures, and otherconditions, a variety of properties can be imparted to these filaments.The tenacity of the filaments should be at least about 10 g/d,preferably at least about 15 g/d, more preferably at least about 25 g/dand most preferably at least about 35 g/d. Similarly, the tensilemodulus of the filaments, as measured by an Instron tensile testingmachine, is at least about 200 g/d, preferably at least about 500 g/d,more preferably at least about 1000 g/d and most preferably at leastabout 1500 g/d. The energy-to-break of the filaments is at least about 8J/g, preferably at least about 25 J/g, more preferably at least about 40J/g and most preferably at least about 50 J/g. These highest values fortenacity, tensile modulus and energy-to-break are generally obtainableonly by employing solution grown or gel filament processes. Highstrength polyethylene fiber known as Spectra® is commercially availablefrom Allied-Signal, Inc.

Similarly, highly oriented polypropylene of molecular weight at least200,000, preferably at least one million and more preferably at leasttwo million, may be used. Such high molecular weight polypropylene maybe formed into reasonably well oriented filaments by techniquesdescribed in the various references referred to above, and especially bythe technique of U.S. Pat. Nos. 4,663,101 and 4,784,820. and U.S. patentapplication Ser. No. 069,684, filed Jul. 6, 1987 (see publishedapplication WO 89 00213). Since polypropylene is a much less crystallinematerial than polyethylene and contains pendant methyl groups, tenacityvalues achievable with polypropylene are generally substantially lowerthan the corresponding values for polyethylene. Accordingly, a suitabletenacity is at least about 10 g/d, preferably at least about 12 g/d, andmore preferably at least about 15 g/d. The tensile modulus forpolypropylene is at least about 200 g/d, preferably at least about 250g/d, and more preferably at least about 300 g/d. The energy-to-break ofthe polypropylene is at least about 8 J/g, preferably at least about 40J/g, and most preferably at least about 60 J/g.

High molecular weight polyvinyl alcohol filaments having high tensilemodulus are described in U.S. Pat. No. 4,440,711, hereby incorporated byreference. Preferred polyvinyl alcohol filaments will have a tenacity ofat least about 10 g/d, a modulus of at least about 200 g/d and anenergy-to-break of at least about 8 J/g, and particularly preferredPV-OH filaments will have a tenacity of at least about 15 g/d, a modulusof at least about 300 g/d and an energy-to-break of at least about 25J/g. Most preferred PV-OH filaments will have a tenacity of at leastabout 20 g/d, a modulus of at least about 500 g/d and an energy-to-breakof at least about 30 J/g. Suitable PV-OH filament having a weightaverage molecular weight of at least about 200,000 can be produced, forexample, by the process disclosed in U.S. Pat. No. 4,599, 267.

In the case of polyacrylonitrile (PAN), PAN filament for use in thepresent invention are of molecular weight of at least about 400,000.Particularly useful PAN filament should have a tenacity of at leastabout 10 g/d and an energy-to-break of at least about 8 J/g. PANfilament having a molecular weight of at least about 400,000, a tenacityof at least about 15 to about 20 g/d and an energy-to-break of at leastabout 25 to about 30 J/g is most useful in producing ballistic resistantarticles. Such filaments are disclosed, for example, in U.S. Pat. No.4,535,027.

In the case of aramid filaments, suitable aramid filaments formedprincipally from aromatic polyamide are described in U.S. Pat. No.3,671,542, which is hereby incorporated by reference. The aramidfilament will have a tenacity of at least about 15 g/d, a modulus of atleast about 400 g/d and an energy-to-break of at least about 8 J/g.Preferred aramid filament will have a tenacity of at least about 20 g/d,a tensile modulus of at least about 500 g/d and an energy-to-break atleast about 20 J/g, and particularly preferred aramid filaments willhave a tenacity of at least about 20 g/d, a modulus of at least about1000 g/d and an energy-to-break of at least about 20 J/g. Most preferredaramid filaments will have a tenacity of at least about 22 g/d, amodulus of at least about 900 g/d and an energy-to-break of at leastabout 27 J/g. For example, poly(p-phenylene terephthalamide) filamentsproduced commercially by Dupont Corporation under the trade name ofKevlar® 29, 49, 129 and 149 and having moderately high moduli andtenacity values are particularly useful in forming ballistic resistantcomposites. Also useful in the practice of this invention ispoly(metaphenylene isophthalamide) filaments produced commercially byDupont under the trade name Nomex.

In the case of liquid crystal copolyesters, suitable filaments aredisclosed, for example, in U.S. Pat. Nos. 3, 975,487, 4,118,372, and4,161,470, hereby incorporated by reference. Tenacities of about 15 to30 g/d, more preferably about 20 to 25 g/d, modulus of about 500 to 1500g/d, preferably about 1000 to 1200 g/d, and an energy-to-break of atleast about 10 J/g are particularly desirable.

A projectile is a body projected by external force and continuing inmotion by its own inertia. It may be a fragment of some larger object,e.g., bullets, engine blades, shrapnel, or may be a large object itself.By large projectile is meant a projectile having at least one dimensionin the range of about 1 to 24 inches (2.54 to 61.0 cm). Typically, thisprojectile will have a weight in excess of about 3 pounds (1.4 kg).Projectiles with a high hardness impacting edge, like tungsten ortitanium, deform so slightly upon impacting an armor system that theytend to cut and tear the system; this is a cutting projectile. By highhardness is meant a projectile having a Rockwell hardness (ASTM D-785)of 35 to 150 or a Brinell hardness of 50 to 800.

By engaging the projectile is meant that the fibers in the networksforming the layer tend to pull out of their network configuration andwrap around the projectile to entangle it--a substantial portion of thefibers are resistant to cutting/abrading by the projectile, and as aconsequence, the projectile is ensnarled by the fibers.

In its broadest aspects, see FIGS. 1 and 1A, the invention is directedto a multi-layered fiber-containing article of manufacture 10 comprisingat least two layers 11 and 12, each of which is comprised of a pluralityof pliable networks of fibers (13 for layer 11 and 14 for layer 12). Themultiple networks of fibers may be stitched together as long as theyremain pliable. By pliable is meant supple enough to bend freely orrepeatedly without breaking.

In the armor system of the first embodiment, which is particularlyeffective in containing large, high velocity cutting projectiles, thefirst layer 11 is arranged to receive the impact from the projectile andengages the projectile to slow the velocity of the projectile. It ispreferred that the first layer 11 comprise a plurality of networks 13selected from the group consisting of an uncoated nonwoven network ofrandomly oriented fibers (as shown in FIGS. 1 and 2) and an uncoated,open knitted network of fibers.

The most preferred first layer for this first armor system comprises aplurality of nonwoven networks of randomly oriented fibers, at least oneof which comprises discontinuous fiber, preferably staple fiber, havinga length ranging from about 0.25 to 10.0 inches (0.63 to 25.4 cm), morepreferably from about 1.0 to 8.0 inches (2.54 to 20.3 cm), mostpreferably from about 2.0 to 6.0 inches (5.1 to 15.2 cm). Generallyspeaking, within the range of 0.25 to 10.0 inch (0.63 to 25.4 cm) fiberlengths, as the fiber length increases, the ability to engage theprojectile, and thus stop/slow the velocity of the projectile,increases.

There are several methods to lay such a completely random anddiscontinuous network of fibers, for example by carding or fluid laying(air or liquid), as are conventional in the art. Consolidation of thenetwork for handling, i.e., bonding of the network of fibers, can occurby any of the following means: mechanically, e.g., needle punching;chemically, e.g., with an adhesive; and thermally, with a fiber to pointbond or a blended fiber with a lower melting point. The preferredconsolidation method is needle punching, alone or followed by one of theother methods.

The most preferred nonwoven network comprising discontinuous fiberlengths is a needle punched felt. This is also the most preferrednetwork for use in the first layer. An alternate first layer for thisarmor system, however, comprises a plurality of knit networks. Thesenetworks can be formed by flatbed knitting yarn into an open knit fabricto form one of the the fibrous networks.

The second fibrous layer 12 dissipates the incoming energy of theimpact, preferably by deformation (netting effect), to prevent totalpenetration by the projectile through the armor system. Deformation canbe measured in one of two fashions, either by the NIJ Standard 0101.03or visually, as set forth in the accompanying examples. The NIJ maximumpermissible deformation is 44 mm. In some European countries, themaximum permissible deformation varies from 20 to 30 mm. This secondlayer 12 preferably comprises a plurality of networks 14 selected fromthe group consisting of a loosely woven network of fibers (see FIG. 1),a tightly knitted network of fibers, a braided network of fibers, and anonwoven network of oriented fibers (see FIG. 2, 14').

A preferred second layer, especially for use in combination with a firstlayer comprising felt networks (combination shown in FIG. 2), comprisesa plurality of nonwoven networks 14' of oriented fibers wherein eachnetwork is comprised of a plurality of sheet-like arrays of untwistedfibers with the fibers aligned substantially parallel to one anotheralong a common fiber direction within each array. The fiber alignmentdirections in selected arrays can be, and preferably are, rotated withrespect to the alignment direction of another array. The arrays arepreferably individually impregnated with a matrix binder and stacked, asis known in the art. See, for example, allowed U.S. patent applicationSer. No. 045,930, filed May 4, 1987, hereby incorporated by reference.It is important that the arrays not be consolidated between networkswith the matrix binder since this will stiffen the layer too much. Analternate nonwoven network of oriented fibers comprises interlacedunidirectional fiber tapes or stitch bonded fiber arrays.

A loosely woven network of fibers is one which has a basket style weaveor equivalent. The fibers of the loosely woven network have fewercrossover points and thus can respond to the impact without breaking inthe networks toward the impact side of the layer. The key to the basketweave is the construction, i.e., the higher the number of ends forweaving, the higher the breaking strength for the fabric. This resultsin a better performance for larger projectiles. If this fabric is usedas the impact face with small projectiles/fragments, the fragments willseparate the fibers to penetrate the impact layer.

The braided network of fibers utilized higher denier fibers. Again, thekey is the loose construction and the higher denier multifilamentsystem, with the same advantage as stated for loosely woven networklayer.

It is preferred that none of the fibrous networks be impregnated otherthan the nonwoven network of oriented fibers because of stiffness. Thelayers of the system must be pliable. For the nonwoven network oforiented fibers, the matrix material employed can comprise one or morethermosetting resins, or one or more thermoplastic resins, or a blend ofsuch resins. As used herein "thermoplastic resins" are resins which canbe heated and softened, cooled and hardened limitless times withoutundergoing a basic alteration, and "thermosetting resins" are resinswhich do not tolerate thermal cycling and which cannot be resoftened andreworked after molding, extruding or casting and which attain new,irreversible properties when once set at a temperature which is criticalto each resin.

Preferred thermosetting resins are urethanes, amino resins, acrylics,alkyds, vinylesters, unsaturated polyesters, epoxies and phenolics.Particularly preferred thermosetting resins are vinylesters, epoxies andphenolics, with vinylesters being the thermosetting resin of choice.

Thermoplastic resins for use in the practice of this invention may alsovary widely. Illustrative of useful thermoplastic resins arepolyurethanes, polyvinyls, polyacrylics, polyolefins, andpolyisoprene-polyethylene-butylene-polystyrene orpolystyrene-polyisoprene-polystyrene block copolymer thermoplasticelastomers, most preferably the latter.

The proportion of matrix to filament in the network is preferably about10 to 30%. The filaments preferably are precoated with the desiredmatrix material prior to being arranged in a network. The coating may beapplied to the filaments in a variety of ways and any method known tothose of skill in the art for coating filaments may be used. In the mostpreferred embodiment of this invention, two such impregnated networksare then continuously cross plied, preferably by cutting one of thenetworks into lengths that can be placed successively across the widthof the other network in a 0°/90° orientation.

For an armor system of the first embodiment wherein the fibers consistessentially of a high molecular weight polyethylene, the preferredconstruction is as follows: for cutting projectiles of any size and forlarge projectiles, the first layer comprises a plurality of, preferablyabout 4 to 100, felt networks each having an areal density of about 4 to100 oz/yd² (0.03 to 0.69 lbs/ft²) and having a needle punch density ofabout 200 to 1800 punches per square inch, and the second layercomprises a plurality of, preferably about 10 to 100, loosely woven(basket weave 8×8) networks having an areal density of about 5 to 35oz/yd² (0.04 to 0.24 lbs/ft²).

For an armor system of the first embodiment wherein the fibers consistessentially of a high molecular weight aramid, the preferredconstruction is as follows: for cutting projectiles of any size and forlarge projectiles, the first layer comprises a plurality of, preferablyabout 4 to 100, felt networks each having an areal density of about 4 to100 oz/yd² (0.03 to 0.69 lbs/ft²) and having a needle punch density ofabout 200 to 1300 punches per square inch, and the second layercomprises either a plurality of, preferably about 10 to 100, looselywoven (basket weave 8×8) networks having an areal density of about 5 to30 ounces/yd² (0.04 to 0.21 lbs/ft²), or a plurality of, preferablyabout 10 to 100, braids having an areal density of about 3 to 30 oz/yd²(0.02 to 0.21 lbs/ft²).

The best hybridized armor system of the first embodiment is as follows:for the first layer, a plurality of, preferably 10 to 80, felt networksconsisting essentially of a high molecular weight polyethylene asdescribed above, and for the second layer, a plurality of, preferably 10to 80, of either braids or loosely woven (basket weave) networksconsisting essentially of an aramid as described above.

The networks of each layer may be stitched together with a fiber,preferably a high strength fiber such as is found in the networksforming the system, in a diamond, square or other pattern known in theart, and the layer then laid like a blanket around the object to beshrouded or shielded, followed by subsequent layers. The layers maythemselves be also stitched together. It is important that the layers ofthe armor system remain pliable after stitching. The layers arepreferably parallel and adjacent to one another; however, it isconsidered part of the present invention to space them apart inparallel.

With reference to FIG. 4, the shroud 20 of the preferred embodiment isdepicted with the first layer 21 closer to the high velocity cuttingimpact projectile threat, i.e., the turbine blade 23, and with thesecond layer 22 between first layer 21 and the nacelle 24, which housesthe engine.

In the armor system of the second embodiment, the first layer isarranged to face the impact from the projectile. It dissipates theenergy upon the impact via the tensile modulus of the fibers and thebreaking strength of the fabric. It is preferred that the first layercomprise a plurality of networks selected from the group consisting of atightly or loosely woven network of fibers, a knitted, preferrablytightly, network of fibers, a braided network of fibers, and a nonwovennetwork of oriented fibers. These constructions are as described for thesecond layer of the first embodiment, except for the tightly wovennetwork of fibers, which can be a plain weave construction, e.g., 17×17,34×34, 56×56, etc. FIGS. 1, 1A, 2 and 2A also depict this system as wellas that of the first embodiment--the layers are simply switched so thatthe impacting layer now becomes the non-impact layer and vice versa.

The second layer of this second embodiment minimizes any deformation ofthe system by the projectile impact to the first layer. And if theprojectile penetrates the first layer, the second layer engages theprojectile by utilizing the high strength and cut resistantcharacteristics of the fibers. It is preferred that the second layer ofthis second embodiment comprise a plurality of networks selected fromthe group consisting of an uncoated nonwoven network of randomlyoriented fibers and an open uncoated knitted network of fibers. Thesenetworks are as described for the first layer of the first embodimentabove.

For an armor system of the second embodiment wherein the fibers consistessentially of a high molecular weight polyethylene, the preferredconstruction is as follows: for projectiles smaller than three poundsthat are not cutting projectiles, the first layer comprises a pluralityof, preferably about 10 to 100, nonwoven networks of resin impregnated0°/90° cross-plied unidirectional monofilament arrays having an arealdensity of about 0.5 to 10 oz/yd² (0.004 to 0.069 lbs/ft²), and thesecond layer comprises a plurality of, preferably about 2 to 50, feltnetworks having an areal density of about 0.5 to 30 oz/yd² (0.004 to0.21 lbs/ft²) and having a needle punch density of about 300 to 1800punches per square inch.

For an armor system of the second embodiment wherein the fibers consistessentially of a high molecular weight aramid, the preferredconstruction is as follows: for projectiles smaller than three poundsthat are not cutting projectiles, the first layer comprises a pluralityof, preferably about 10 to 100, nonwoven networks of resin impregnated0°/90° cross-plied unidirectional monofilament arrays having an arealdensity of about 0.5 to 10 oz/yd² (0.004 to 0.069 lbs/ft²), and thesecond layer comprises a plurality of, preferably about 2 to 50, feltnetworks having an areal density of about 0.5 to 30 oz/yd² (0.004 to0.21 lbs/ft²) and having a needle punch density of about 200 to 1300punches per square inch.

The networks of each layer may be stitched together as in the firstembodiment, and the layer then laid like a blanket around the object tobe shrouded or shielded, followed by subsequent layers. Again, thelayers may themselves be stitched together or spaced apart in parallel.It is also important that the layers of the armor system remain pliablefor this embodiment.

For an armor system 15 of the third embodiment (see FIG. 3), thepreferred construction is a first felt layer 16 comprising highmolecular weight polyethylene fiber, aramid fiber, or a combination ofthe two; a second loosely woven (basket weave) layer 17 comprising highmolecular weight polyethylene fiber, aramid fiber, or a combination ofthe two; and a third felt layer 18 like the first. The number ofnetworks, their areal densities, and their needle punch densities are asindicated above for the preferred first armor embodiment.

Studies of ballistic armor frequently employ a 22 caliber, non-deformingsteel fragment of specified weight, hardness and dimensions (Mil-Spec.MIL-P-46593A(ORD)). The protective power of a structure is normallyexpressed by citing the impacting velocity at which 50% of theprojectiles are stopped, and is designated the V₅₀ value.

The following examples are presented to provide a more completeunderstanding of the invention. In the Examples, the impact cam cut testis performed using the method and BETATEC.sup.˜ testing apparatus ofU.S. Pat. No. 4, 864,852, hereby incorporated by reference. The testinvolves repeatedly contacting a sample with a sharp edge until thesample is penetrated by the cutting edge. The higher the number ofcutting cycles (contacts) required to penetrate the sample, the higherthe reported cut resistance of the sample. During testing, the followingconditions were used, unless otherwise specified: 90 grams cuttingweight, mandrel speed of 50 rpm, rotating steel mandrel diameter of 19mm (0.75 inch), cutting blade drop height of about 8.9 mm (0.35 inch),use of a single-edged industrial razor blade (Red Devil brand) forcutting, cutting arm distance from pivot point to center of blade beingabout 15.2 cm (about 6 inches). The impact cam cut test allows for acutting edge to abruptly impact a sample. The networks were cut testedafter cutting samples 2×3.5 inches and wrapping them on the testermandrel. The samples were held on the mandrel with 2 band clamps placedover each end.

The level of cut resistance required of the cut resistant networks ofthe present invention is at least 5 cycles of the impact cam cut test.Because of the openness of a loosely knit network, this test is not agood test for cut resistance. However, if the knit yarns are cutresistant then it would follow that the network would possess therequisite cut resistance for this invention.

In Examples 5-16, the armor systems were tested with a gas gun by theImpact Physics Laboratory at the University of Dayton, Ohio, for theGeneral Electric Company. The projectile was a titanium blade 2 incheswide, 6 inches long and 3/16 inch thick, and weighing 183 g. The softarmor systems of those examples were 12×18 inches, and a one inchboundary of the system along its perimeter was impregnated with an epoxyresin to make it rigid. The system was then attached to a metal framewith bolts at the four corners and in the rigid boundary. The system inthe frame was inclined towards the gas gun at an angle of approximately30° from the axis of the gas gun's barrel. It is believed that the testsample was approximately 10 feet from the barrel of the gun. The bladewas shot into the middle of the system either at a velocity of 430ft/sec (level 1) or 600 ft/sec (level 2). Failure meant that theprojectile completely penetrated the system.

It should be understood that the armor systems of Examples 5-19, theprojectile, and the test system were all scaled down due to theoverwhelming expense involved in replicating the high velocity cuttingimpact of a large projectile such as a turbine blade. The projectiledescribed above simulates a large projectile, i.e., one weighing about 3pounds and flying at a velocity of about 3000 feet per second.

EXAMPLES 1-2 (COMPARATIVE)

In Example 1, 32 networks of Spectra® 1000 8H satin weave fabric style985, commercially available from Allied-Signal Corporation, werestitched together in a diamond shape pattern to produce a test samplehaving an areal density of 176 oz/yd² (1.22 lb/ft²). In Example 2, a 25network system was produced just as in Example 1, but having an arealdensity of 138 oz/yd² (0.960 lb/ft²).

Both of these systems were submitted to a 22 caliber 17 grain FSPevaluation test according to MIL-STD-662E. In Example 1, a V₅₀ value of1797 fps was obtained, while in Example 2, a V₅₀ value of 1611 fps wasobtained. Visual observation of the non-impact side of these samplesrevealed significant deformation (or deflection) of each of the systems.

EXAMPLES 3(COMPARATIVE)-4

One layer was comprised of 5 felt networks each having an areal densityof about 8 oz/yd² (0.0556 lbs/ft²) and having a needle punch density ofabout 500 punches per square inch. The fiber used in these felt networkswas Spectra® 1000 2.75 inch (7.0 cm) staple, commercially available fromAllied-Signal Corporation. The fiber was carded and cross lapped to a 60inch (1.52 m) width. The carded webs were stacked up by the cross lapperto produce an 8.0 ounce per square yard fabric, as is known in the art.The fabric was tacked and needled (300 punches per square inch with a#10 needle), and then taken up into a roll. The off line needle punchingused a #100 needle and a needle punch density of 200 punches per squareinch.

The other layer was comprised of 20 networks of Spectra® 1000 8H satinweave fabric style 985, commercially available from Allied-SignalCorporation, and having an areal density of about 5.5 oz/yd² (0.038lb/ft²) .

The two layers were stitched together in a diamond shape pattern. Thetotal areal density for the system was 1.037 lb/ft².

In Example 3, the felt layer was facing the incoming projectile. Thesample was submitted to a 22 caliber 17 grain FSP test following MILSTD-662E. A V₅₀ of 1676 fps was obtained. Visual observation of thenon-impact side of the sample revealed significant deformation of thesystem.

In Example 4, the fabric layer was facing the incoming projectile fortesting in accordance with Example 1. A V₅₀ of 1892 fps was obtained.Visual observation of the non-impact side of the sample revealed littledeformation of the system, and it was estimated that deformation of thesystem was approximately 80% less than that for Example 3.

EXAMPLE 5 (COMPARATIVE)

In this example, 20 networks of Spectra® 1000 fabric style 954, 56×56plain weave (185 denier), commercially available from Allied-SignalCorporation, were put together to produce a test sample having an arealdensity of 54.0 oz/yd² (0.37 lb/ft²). At level 1, the system failed.

EXAMPLE 6 (COMPARATIVE).

Example 5 was repeated, except that 30 networks of fabric were used, andthe total areal density of the sample was 80.3 oz/yd² (0.55 lb/ft²). Atlevel 1, this system also failed.

EXAMPLE 7 (COMPARATIVE)

In this example, 28 networks of Spectra Shield (made from Spectra 1000and commercially available from Allied-Signal Corporation) wereconsolidated into a rigid test sample having an areal density of 0.748lb/ft². At level 1, this system stopped the projectile.

EXAMPLE 8 (COMPARATIVE)

Example 7 was repeated, except that 42 networks of Spectra Shield wereconsolidated into a rigid test sample having an areal density of 1.12lb/ft². At level 2, this system failed.

EXAMPLE 9 (COMPARATIVE)

In this example, 18 networks of Spectra® 900 fabric style 913 (1200denier), basket weave 8×8, 48×48, commercially available fromAllied-Signal Corporation, were put together to produce a test samplehaving an areal density of 1.91 lb/ft². At level 2, this system stoppedthe projectile; however, visual inspection of the non-impact side of thesample showed significant deformation of the system.

EXAMPLE 10

One layer was comprised of 4 felt networks each having an areal densityof about 5 oz/yd² (0.0345 lb/ft²) and having a needle punch density ofabout 500 punches per square inch, as previously described. The fiberused in these felt networks was Spectra® 1000 2.75 inch (7.0 cm) staple,commercially available from Allied-Signal Corporation.

The other layer was comprised of 17 networks of Spectra® 900 basketweave (8×8) fabric style 913, commercially available from Allied-SignalCorporation, and each having an areal density of about 15.5 oz/yd²(0.106 lb/ft²). The total areal density for the system was 1.97 lb/ft².

These two layers were formed into a system for testing, and the feltlayer was facing the incoming projectile. At level 2, this systemperformed better than Example 9 above, and without significantdeformation.

EXAMPLE 11 (COMPARATIVE)

In this example, 42 networks of Kevlar® 29 fabric style 328, plainweave, 17×17, 1420 denier, commercially available from DuPontCorporation, were put together to produce a test sample equivalent byweight to the sample in Example 9, i.e., 1.95 lb/ft². At level 2, thissystem stopped the projectile; however, visual inspection of thenon-impact side of the sample showed significant deformation of thesystem.

EXAMPLE 12

One layer was comprised of a plurality of Spectra® 1000 (2.75 inchstaple) felt networks. The other layer was comprised of a plurality ofKevlar® 29 fabric networks as described in Example 11.

It is believed that the number of felt networks numbered between 9 and 3and that the felt layer had a total areal density in the range of about44.96 to 14.89 oz/yd² (0.308 to 0.102 lb/ft²). It is believed that thenumber of fabric networks numbered between 35 and 40 and had a totalareal density of about 237.96 to 271.53 oz/yd² (1.63 to 1.86 lb/ft²).The total areal density for the system is believed to have been about284.7 oz/yd² (1.95 lb/ft²), which is comparable to the systems ofExamples 9 and 10.

The two layers were formed into a system for testing with the felt layerfacing the incoming projectile. At level 2, this system performedequivalent to Example 10 above.

EXAMPLE 13

One layer was comprised of a plurality of Kevlar® 29 (2.75 inch staple)felt networks. The other layer was comprised of a plurality of Spectra®900 basket weave (8×8) fabric style 913 networks, commercially availablefrom Allied-Signal Corporation.

It is believed that the number of felt networks numbered between 10 and4 and that the felt layer had a total areal density of about 50 to 20oz/yd² (0.342 to 0.137 lb/ft²). It is believed that the number of fabricnetworks numbered between 15 and 17 and had a total areal density ofabout 102.0 to 115.6 oz/yd² (1.59 to 1.80 lb/ft²). The total arealdensity for the system is believed to have been about 284.7 oz/yd² (1.95lb/ft²), which is comparable to the systems of Examples 9 and 10.

The two layers were formed into a system for testing with the felt layerfacing the incoming projectile. At level 2, this system had aperformance similar to Example 10 above.

EXAMPLE 14

In this example, the test sample was made with a plurality of braidednetworks formed from Spectra® 1000, 650 denier yarn. The total arealdensity of the system is believed to have been about 284.7 oz/yd² (1.95lb/ft²).

At level 2, this system had good performance.

EXAMPLE 15

One layer is comprised of a plurality of Spectra® 1000 (2.75 inch) feltnetworks having a total areal density of about 15 to 60 oz/yd² (0.1 to0.4 lb/ft²).

The other layer is comprised of a plurality of Spectra® 1000, 650denier, braided networks having a total areal density of about 270 to226 oz/yd² (1.85 to 1.55 lb/ft²).

The two layers are formed into a system having a total areal density ofabout 284.7 oz/yd² (1.95 lb/ft²) for testing with the felt layer facingthe incoming projectile. At level 2, this system is expected to performbetter than Example 14 above.

EXAMPLE 16

In this example, the test sample was made with a plurality of braidednetworks formed from a composite yarn. The composite yarn was formed bylaying a 650 denier Spectra® 1000 fiber parallel to a 400 denier glassfiber and then overwrapping the two in one direction with a 650 denierSpectra® 1000 fiber followed by overwrapping in the opposite directionwith a second 650 denier Spectra® 1000 fiber. The total areal density ofthe system is believed to have been about 284.7 oz/yd² (1.95 lb/ft²) .

At level 2, this system had good performance.

EXAMPLE 17

One layer is comprised of from about 10 to 4 networks formed by flatbedknitting (open knit) a composite yarn as described in Example 16. Thetotal areal density of the layer is about (0.1 to 0.4 lb/ft²).

The other layer is comprised of from about 15 to 17 networks of Spectra®900 basket weave (8×8, 48×48) fabric style 913 networks having a totalareal density of about 102.0 to 115.6 oz/yd² (1.59 to 1.80 lb/ft²). Thetotal areal density for the system should be about 284.7 oz/yd² (1.95lb/ft²).

The two layers are formed into a system for testing with the knittedlayer facing the incoming projectile. At level 2, it is anticipated thatperformance of the system will be good.

EXAMPLE 18

One layer is comprised of from 10 to 4 networks of Spectra® 1000 (2.75inch staple) felt networks having a total areal density of about 50 to20 oz/yd² (0.342 to 0.137 lb/ft²).

The other layer is comprised from 48 to 52 knitted (tighter knit)networks of the composite yarn of Example 16 having a total arealdensity of about 102.0 to 115.6 oz/yd² (1.59 to 1.80 lb/ft²). The totalareal density for the system is believed to be about 284.7 oz/yd² (1.95lb/ft²).

The two layers are formed into a system for testing with the felt layerfacing the incoming projectile. At level 2, it is anticipated thatperformance will be good.

EXAMPLE 19

One layer is comprised of from 10 to 4 networks of Spectra® 1000 (2.75inch staple) felt networks having a total areal density of about 50 to20 oz/yd² (0.342 to 0.137 lb/ft²).

The other layer is comprised of from about 55 to 61 networks of SpectraShield (made from Spectra® 1000 and commercially available fromAllied-Signal Corporation) having a total areal density of about 102.0to 115.6 oz/yd² (1.59 to 1.80 lb/ft²). The total areal density for thesystem is believed to be about 284.7 oz/yd² (1.95 lb/ft²).

The two layers are formed into a system for testing with the felt layerfacing the incoming projectile. At level 2, it is anticipated thatperformance will be good.

EXAMPLE 19

In this example, needle punched felt networks of high molecular weightpolyethylene fiber, polyester fiber and nylon fiber were tested forimpact cam cut performance. The polyethylene felt network was asdescribed in Example 4 (5 dpf) and had a cut resistant of 10.7 cycles onthe impact cam cut test previously described. Two 4 oz/yd² polyesterfelts (1 inch, 6 dpf) lightly tacked together, were also tested and hada cut resistance of 4.7 cycles on the same test. A nylon felt (4 oz/yd²,2 inches, 3.5-4 dpf) was tested and had a cut resistance of 1 cycle onthe test. The cut test data represents the average of at least 6 tests.It is believed that aramid felts, particularly poly(p-phenyleneterephthalamide), would have an impact cam cut resistance in excess of 5cycles.

DISCUSSION

From the above examples, it can be seen that the two layer armor systemsof the present invention for large, high velocity cutting projectilesperformed better than the single layer systems. Within these two layerarmor systems, it can be seen that the combination of felt networks forthe first layer and braided networks for the second layer were the best.

Examples 1 through 4 show the importance of the second layer of the twolayer armor system of the present invention for resistance to smallerprojectiles. With felt networks forming the second layer (away from theimpacting projectile), deformation is minimized and complete penetrationof the system stopped.

We claim:
 1. An armor system comprising a first pliable fibrous layerand a second pliable, cut resistant fibrous layer, the first layer beingarranged to receive a high velocity impact from a projectile prior tothe second layer and being resistant to said impact, the second layerminimizing any deformation of the system by the projectile impact to thefirst layer and engaging the projectile upon penetration by theprojectile of the first layer, both of said first and second layerscomprising fibers having a tensile modulus of at least about 200 g/d,and an energy-to-break of at least about 8 J/g and a tenacity equal toor greater than about 10 g/d, wherein the first layer comprises aplurality of nonwoven networks of oriented fibers, and the second layercomprises an uncoated needle punched felt of discontinuous fibers havinga length ranging from about 0.25 to 10.0 inches (0.63 to 25.4 cm). 2.The system of claim 1, wherein each of the nonwoven networks of orientedfibers is comprised of a plurality of sheet-like arrays of said fibers,said fibers in each array being aligned substantially parallel to oneanother in each array along a common fiber direction within each array.3. The system of claim 2, wherein the fiber alignment directions inselected arrays are rotated with respect to the alignment direction ofanother array.
 4. The system of claim 2, wherein said arrays areindividually coated with a matrix binder.
 5. The system of claim 1,wherein the fibers are selected from the group consisting of polyolefinfibers, polyvinyl alcohol fibers, aramid fibers, polyacrylonitrilefibers, liquid crystalline fibers, and mixtures thereof.
 6. The systemof claim 1, wherein the fibers are polyethylene fibers.
 7. The system ofclaim 1, wherein the fibers are aramid fibers.